Packet Transport Network (PTN) techniques are connectivity-oriented network techniques with core spirits being packet-oriented general switching techniques. PTN techniques have something in common with traditional Synchronous Digital Hierarchy/Multi-service Transfer Platform (SDH/MSTP) in physical architecture in an aspect of networking, i.e., both have three network layers including a core layer, a convergence layer and an access layer, and ring networks, chain networks, mesh networks and the like can be networked.
Depending on scales of networks, for a network having relatively small quantity of nodes and relatively low traffic, its access layer can be networked as a ring using a Gigabit Ethernet (GE), its convergence layer can be networked as a ring using a 10 Gigabit Ethernet (10GE), and its core layer can also be networked as a ring using a 10GE due to its relatively low traffic. Some networks have only two layers, i.e., an access layer and a core convergence layer; for a network having relatively large quantity of nodes and relatively high traffic, its access layer can be networked as a ring using a GE, its convergence layer can be networked as a ring using a 10GE, but it has relatively high traffic and its 10GE ring of the convergence layer is nearly full, thus if the core layer is also networked as a ring using a 10GE, then the bandwidth can not be converged, and in this case, it can be constructed in a direct way, such as being networked as a mesh network architecture.
The core layer takes responsible for providing interstation circuits between core nodes and scheduling various services, thus the core layer should have high volume service scheduling capability and multi-service transmission capability. The core layer can be networked as a ring using a 10GE with a number of nodes being 2 to 6; and it can also be networked as a mesh network.
The convergence layer takes responsible for converging and grooming various services within a certain area, thus the convergence layer should have relatively high service convergence capability and multi-service transmission capability, and it can be networked as a ring using a 10GE with a number of nodes preferably being 4 to 8.
The access layer should have flexible and fast multi-service access capability. It can be networked as a ring or chain, with a number of nodes on the ring being no more than 15 and a number of nodes on the chain being no more than 3.
When networks are planed and constructed, above networking rules can be substantially complied with, but during development and evolution of these networks, there tends to be excessive nodes on a ring (or chain) due to various reasons, thus network structure optimization is an important part of PTN optimization. When networks have relatively large scale, it is difficult to divide artificially all links (and then nodes of respective links) to various network layers of respective layered networks, this makes it difficult to calculate the networking type of each layered network and to count the number of nodes on each ring (or chain) of the whole network, thus bringing too much difficulty to the network optimization.
In fact, besides PTN networks, other types of networks also encounter the same problem that it is difficult to divide artificially all links (and then nodes of respective links) to various network layers of respective layered networks when the networks have relatively large scale. However, as to the problem in relevant techniques that it is difficult to divide artificially all links (and then nodes of respective links) to various network layers of respective layered networks when the networks have relatively large scale, there is no effective solution proposed so far.